Batten

A batten is a narrow strip of wood used functionally rather than decoratively -- bracing a panel against cupping from behind, spacing boards apart in a stack for air-drying (in which context battens are usually called "stickers"), or serving as a temporary straightedge clamped down as a saw guide. The common thread across all these uses is that a batten is doing structural or supporting work, generally hidden or at least secondary, rather than being a finished, visible surface in its own right.